Diversion from tolls will be worse than WSDOT estimates because figures considered in the state's environmental- impact statement don'tt factor in a new connector that will link Elliott and Western avenues with Alaskan Way, which would give drivers another option to avoid the tunnel. As a result, the report estimates only 38,000 drivers per day will use the tunnel with tolls, compared to the current 110,000 vehicles that take the viaduct. WSDOT estimates that under the most likely toll scenario, about 41,000 vehicles would use the tunnel. If there were no tolls, about 86,000 vehicles per day would take the tunnel and the remainder of today's viaduct traffic would use a new surface Alaskan Way.

Toll diversion would require more investment in transit: The report estimates that a robust transit and traffic demand management have the potential to shift 15,000 daily trips away from driving and to transit and other high occupancy modes. This is approximately equivalent to the amount of tolling diversion traffic projected to enter the city’s surface streets each day

Regional tolling: To keep traffic from diverting to avoid tolls on the Highway 99 corridor, the state might want to more quickly move to a regional tolling program. "A congestion pricing program could, if implemented effectively, also act as a means to balance regional traffic flow," the report says. "In the case of the SR 99 deep bored tunnel project, the proposed tolling strategy only partially meets regional goals in that it establishes a user fee for this section of roadway. A more comprehensive approach, reached through a cooperative effort by the city and the state, is needed to ensure that the longer-term strategy carefully laid out in transportation 2040 (plan) is not undermined."

The report's conclusion is that mitigation required to keep traffic moving through downtown with a tolled tunnel seems to defeat the purpose of replacing the Alaskan Way Viaduct with a tunnel. The report hits many of Mayor Mike McGinn's talking points in opposition of the tunnel plan, and advocates for the so-called surface/transit option, which would widen Interstate 5, invest in transit and traffic demand management to handle traffic instead of building a new highway.

But, the "Let's Move Forward" coalition sent out a news release Thursday questioning the report's credibility. It points out the same consultants testified before the City Council in January that a surface/transit option would nearly double the impact of cars traveling downtown. They quote Tim Payne with Nelson/Nygaard Consulting Associates, during Jan. 25 testimony to the Seattle City Council:

"Roughly the amount of increased traffic on downtown surface streets is about twice what the tolling diversion numbers are looking at here. You’re looking at an increase on downtown surface streets, and that’s from Alaskan Way to I-5, not including I-5, is about roughly 50,000 a day…I-5 takes a much larger share because the assumption is there is no bypass, everything is either on the surface, on I-5 or the east of I-5, so we’re absorbing roughly 110,000 cars a day…”

Let’s Move Forward, a coalition of business, labor and community groups that support building the tunnel, also cites from e-mails obtained through public records requests that show an exchange between Payne and SDOT Director Peter Hahn in which Hahn seems to disagree: “This has to be cleared up because absent any further clarification it appears that the answer can be reduced to ‘If you think the tunnel tolling diversion is bad, the surface option is twice as bad."

And then Payne responds to Hahn, Jan. 26, 2011: “In the end, with the surface transit alternative, there was always the need to explain where the 98,000 to 110,000 vehicles per day that are on SR 99 move when SR 99 is no longer present…Pioneer Square was always a hot spot, based on the modeling, of the surface transit alternative.”

They also released an excerpt from another e-mail from Hahn to McGinn’s staffer Ethan Raup and City Councilman Mike O’Brien in which he says: “We are asking Tim and Tom (another Nelson\Nygaard consultant) and the rest of the NN team working for us to explain this more thoroughly and avoid the facile conclusion that surface option is twice as bad as the worst diversion case. However…SDOT staff explained that there was going to be more traffic on city streets with the surface option – it’s not like I-5 and huge transit were going to make it all disappear.”

"In the agreements, we recognize that tolling is part of the project and that the state will work with the city during the tolling implementation on strategies to minimize the effects," Rasmussen said. "Perhaps this study goes into more about what has to be done and will help us work with the state to minimize the effects of tolling if people choose not to use the tunnel."

"Hopefully, it's intended to inform the process rather than just be another effort on the part of the mayor to undermine the project," he said.